Do you have the Auto-Disk or the Pro Auto-Disk? I have the Pro Auto-Disk and just made up a bunch of .45 ACP using 5.0 gr of Unique with very consistent metering. I think that was using the .66 cc hole, and Lee makes disks that go down as low as .30 cc. If you'd like, I could throw some smaller charges of Unique and see how it does.
I think there's a coating on the lower half of the Pro that's missing on the standard, and the brass nuts on the Pro do a better job of holding the halves together.